This invention relates to an improved interiorly located, rotating, self sharpening, replaceable digging tooth apparatus and method.
The provision of digging teeth on large earth movers has been known in the art for quite some time. For example, a box type cap to be placed over shanks on an excavating bucket has been designed that provides a wedged shaped digging tooth for excavation. An example of such a tooth is disclosed in Morrison, U.S. Pat. No. 2,050,014. Other examples, such as Hensley, U.S. Pat. No. 3,444,633, and Stepe, U.S. Pat. No. 3,623,247, also disclose coverings for shanks of excavating buckets with tooth-like devices. The supposed improvements of these devices were in the nature of forming a tight fit with the shank so that the tooth would not work its way off of the shank once placed in position. Other patents have been issued which address the problem of replacement of these teeth, that are highly subject to wear, by various "quick change" means such as disclosed in Lukavich U.S. Pat. No. 3,851,413 and Johansson et al. U.S. Pat. No. 4,414,764. Further, at least one patent, Hemphill, U.S. Pat. No. 4,098,013, was issued for a "digging tooth with replaceable cutting edge". This invention addressed the problem of maintaining a sharp digging edge by means of providing a replaceable "nose piece" that was placed over the digging tooth for a backhoe bucket and which could be replaced whenever the cutting edge thereon became worn.
In today's construction industry, most dirt, rock, sand, etc., is excavated by backhoes, trackhoes and rippers. To dig a ditch for underground utilities or excavate for a highrise foundation, for instance, some sort of excavator or ripper is used. These excavators and rippers are made world wide and are composed generally of a frame, motor, tires or tracks, extended arm, hydraulic system to transfer power from the motor to the arm and a mounting device so that something can be attached to the end of the hydraulic powered arm to scoop up and hold the material. Normally, a "bucket" is mounted to the arm. Buckets come in various shapes and sizes. Narrow buckets are used to dig a narrow utility ditch, for instance, and wide and deep buckets are used to excavate large volumns of materials for a pit or a large foundation area.
On the cutting edge of the bucket are "shanks". Shanks are usually welded and permanently attached to the bucket and are used as a mount for "teeth". Teeth are mounted to the shanks and have sharp edges that are supposed to cut through material to be excavated and are designed to be replaceable when worn out. In fact, digging teeth of prior art design wear out at a rapid and costly rate. The reason for this is that in order to dig anything except soft, loose material, that is, in order to dig any type of hard material such as rock, a pointed tooth must be present on the bucket. A drawback with the digging teeth known in the art is that, although some, but not all, teeth are pointed, the points or edges do not hold up long in any kind of hard, abrasive soil or rock digging. Typically, the rock work dulls teeth very quickly and the edge of present devices is lost which results in lost production time while the machine is stopped in order to change and replace dulled teeth. A further drawback with digging teeth known in the art is that, in order to prevent the point from being broken off, the devices are designed so that the stress of digging runs away from the point to the sides rather than to the larger, stronger central body of the tooth. Additionally present designs cause wear and fatigue of the tooth and its mating surface so that often these teeth fall off their mount. A still further drawback of the digging teeth known in the art is that, because of the fact that these teeth wear out so quickly, digging machines must be shut down and considerable time spent to replace worn teeth which results in a major reoccuring expense and repeated production loss over short periods of time. The fact that the digging teeth will not hold up to abrasive conditions, while all the rest of the machine will, is therefore very costly to the equipment owner.
Thus, there is a need in the art for providing a digging tooth that presents a constantly sharp point to the material being excavated, that can bear the stress of digging hard material without weakening its attachment and which is easily replaceable when necessary. It, therefore, is an object of this invention to provide an improved digging tooth that is self sharpening so that the life of each individual tooth is considerably prolonged. It is a further object of this invention to provide a digging tooth that is interiorly located in a secured position within a driving mechanism with much of the same advantages that a human tooth has over a cap. It is a further object of this invention to provide a digging tooth that can rotate within its interiorly located position so that much of the stress of cutting is avoided and so that the rotation enhances and assists the self sharpening of the tooth while in use. Yet another object of this invention is to provide a digging tooth that, when necessary, is extremely easy to replace, so that the absolute minimum amount of down time to the working machine results from the replacement process.